The most common reason for impaired vision after uneventful cataract surgery in otherwise healthy eyes is the development of posterior capsule opacification (PCO). PCO is a physiological change (thickening, opacification and clouding) of the capsular bag expected after cataract surgery, because the lens epithelial cells (LECs) undergo hyperplasia and cellular migration. PCO is treated with Nd:YAG capsulotomy, a quick outpatient procedure that uses a laser to open a central hole in the posterior capsular bag.